Japanese Patent JPH0376707

B2

PURPOSE:To detect a flaw with a high accurcy and with a high efficiency by once irrespective of the quality of a defect by providing two AC magnetic field generators provided opposingly to be symmetrical to the center of a cylindrical material to be inspected, which is carried in the longitudinal direction, an axial direction magnetic field generator, and a magnetic field detector which is rotatable around the material to be inspected. CONSTITUTION:Two magnetic poles 2a, 2b provided opposingly to be symmetrical to the center of a material to be inspected 1 are fixed and provided on a fixed drum 31, and an orthogonal AC magnetic field is generated alternately. Ring-like solenoids 5, 5 are fixed and provided on supporting disks 34, 35 having a through-hole concentrical to the drum 31, and a magnetic field of an axial direction is generated. A motor 40 is driven to rotate, a rotating body 38 is rotated through pulleys 42, 41, a timing belt 43 and a bearing 37, and when a steel pipe 1 is carried, the lower face of a sensor holder 45 abuts on the outside circumferential surface, and a magnetic field detector contained in the sensor holder 45 moves spirally on the outside circumferential surface of the steel pipe 1 and detects a flaw on the surface. Accordingly, a flaw detection is executed with a high accuracy and with a high efficiency by once irrespective of a quality of a defect.

HIROTA TETSUYA
HIROSHIMA TATSUO

JP10227483A

December 06, 1991

June 07, 1983

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SUMITOMO METAL IND

G01N27/82; G01N27/83; G01N27/90

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